1. Field of the Invention
The present invention relates to a short-distance communication using visible light, and more particularly to a short-distance communication method and an apparatus using visible light that reduce noise caused by ambient light.
2. Description of the Related Art
Short-distance communication using a wireless terminal is generally achieved using infrared light. A wireless communication system using infrared light is usually used in Peer to Peer (P to P) communication, wherein each wireless terminal includes an infrared light transceiver mounted on the terminal. This type of terminal have a transmitter including a Light Emitting Diode (LED) for carrying out infrared light transmission and a light modulator, and a receiver including a Photo Diode (PD) and a demodulator.
The infrared light communication is processed at several Mbps and thus takes a long time to transmit contents. In addition, it is difficult to make an infrared light connection due to a close proximity requirement between terminals. Currently, the beam divergence of a transmitter specified by the Standards Organization is 30 degrees. If a beam divergence is away from the specified value, a normal communication using infrared light cannot be accomplished. To this end, short-distance communication systems using visible light have been developed.
Normally, conventional infrared light communication has disadvantages in that it is difficult for users to make an infrared light connection because it has a narrow beam divergence for an infrared light connection, and also there is no means for checking if an infrared light connection is made or not during operation. However, in Visible Light Communication (VLC) using visible light, it is possible to make a connection link easily by virtue of a broad transmission angle of a transmitter and to confirm the connection by virtue of the visible light. Accordingly, it is expected that a system using visible light will dominate the short-distance communication systems in the future. In order to make a wireless terminal support such a short-distance communication system using the visible light, it is necessary to provide a wireless terminal with a transceiver to achieve a short-distance communication using visible light.
In the short-distance communication using visible light, the most difficult problem is to remove noise caused by ambient light. Although visible light communication uses three wavelengths corresponding to green, blue, and red, the ambient light acts as noise.